The invention relates to a hydraulic tensioning element for a traction mechanism drive with a cylinder, a piston that is displaceable in the axial direction and that is guided in the cylinder, a spring element arranged between the cylinder and piston, a pressure space formed in the cylinder, and a supply space formed in the piston for a hydraulic fluid and a valve that allows hydraulic fluid to be exchanged between the pressure space and the supply space as a function of an actuating movement of the piston.
Hydraulic tensioning elements are used in traction mechanism drives for internal combustion engines and are used for tensioning a traction mechanism, for example, a belt or a chain. The tensioning element includes a cylinder that is formed as a stationary and pivotally arranged housing part, and also a piston that is connected directly or indirectly to a tensioning roller. Spring means are arranged between these elements. The spring means could be constructed as a helical compression spring.
From DE 10 2004 047 450 A1, such a hydraulic tensioning element is known. When the piston rod is moved relative to the cylinder, a volume exchange of the hydraulic fluid is carried out between a pressure space in the cylinder and a supply space in the piston, wherein the direction of flow is dependent on the actuating movement of the piston rod. For a movement of the piston rod in the direction of the pressure space, hydraulic fluid can escape into the supply space via a leakage gap set between the piston rod and the cylinder bushing. For a reverse actuating movement of the piston, the hydraulic fluid flows from the supply space into the pressure space via a valve arranged in the base of the pressure space.
Before mounting on an internal combustion engine, the hydraulic tensioning element must be tensioned by the compression of the spring and must be secured in this position. Here, if the mounting tool slips, the piston snaps out of the cylinder due to the effect of the energy stored in the compression spring, wherein, in individual cases, this could even lead to damage to the tensioning element.